US5022018A - System for applying a perpendicular magnetic field to the illuminated side of a magneto-optic medium - Google Patents

System for applying a perpendicular magnetic field to the illuminated side of a magneto-optic medium Download PDF

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Publication number
US5022018A
US5022018A US07/311,457 US31145789A US5022018A US 5022018 A US5022018 A US 5022018A US 31145789 A US31145789 A US 31145789A US 5022018 A US5022018 A US 5022018A
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United States
Prior art keywords
housing
recording
electromagnet
recording medium
light
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US07/311,457
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English (en)
Inventor
Peter J. Vogelgesang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Co
Original Assignee
Minnesota Mining and Manufacturing Co
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Publication date
Application filed by Minnesota Mining and Manufacturing Co filed Critical Minnesota Mining and Manufacturing Co
Priority to US07/311,457 priority Critical patent/US5022018A/en
Assigned to MINNESOTA MINING AND MANUFACTURING COMPANY, A CORP. OF DE reassignment MINNESOTA MINING AND MANUFACTURING COMPANY, A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: VOGELGESANG, PETER J.
Priority to CA002008019A priority patent/CA2008019A1/en
Priority to DE69016055T priority patent/DE69016055D1/de
Priority to EP90301485A priority patent/EP0383526B1/de
Priority to KR1019900001722A priority patent/KR900013473A/ko
Priority to JP2035070A priority patent/JPH02247849A/ja
Application granted granted Critical
Publication of US5022018A publication Critical patent/US5022018A/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/1055—Disposition or mounting of transducers relative to record carriers
    • G11B11/10552—Arrangements of transducers relative to each other, e.g. coupled heads, optical and magnetic head on the same base
    • G11B11/10554—Arrangements of transducers relative to each other, e.g. coupled heads, optical and magnetic head on the same base the transducers being disposed on the same side of the carrier
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/10532—Heads
    • G11B11/10534—Heads for recording by magnetising, demagnetising or transfer of magnetisation, by radiation, e.g. for thermomagnetic recording
    • G11B11/10536—Heads for recording by magnetising, demagnetising or transfer of magnetisation, by radiation, e.g. for thermomagnetic recording using thermic beams, e.g. lasers

Definitions

  • This invention relates to erasable optical recording systems, particularly so-called magneto-optical recording systems.
  • High density optical recording systems which may be used for recording and playing back information are well known in the art.
  • Current practice in the optical recording field can be broadly distinguished into three categories, the classification being largely dependent on the physical and chemical characteristics of the information carrying media. Common to all three categories is the ability of each system to have the information stored on the media to at least be “read” or “played back” by irradiating selected areas of the media with a highly focused source of light, usually a laser. Changes in the transmission or reflection of the laser beam caused by the presence or absence of recorded information on the media is detected by suitable optical sensors. The three categories are differentiated by the media's response to radiation. "Read Only” as, for example, in Compact Disk technology, wherein all the information on the disk is pre-recorded.
  • WORM Write-Once, Read (Mainly)
  • the third consists of media which can be written upon and read back by laser, but can also be erased (by the laser), in the presence of a suitable magnetic field, and which then can be reused.
  • This invention relates generally to the "erasable" optical recording systems, known in the art as magneto-optical recording systems, and in which the media is described as magneto-optic media.
  • a magneto-optic recording medium is a magnetic material which causes the polarization angle of laser light to be changed when it is reflected from or transmitted through a recorded spot.
  • the magneto-optic media is vertically magnetized in the same direction across the entire recording surface.
  • the direction of magnetization of the media is reversed at the point of incidence of the laser beam due to the presence of a vertical magnetic field of a given strength and polarity and heating induced by a laser. Illumination from a playback laser beam of lower power reflected from this area will show a polarization angle change, which is detectable by suitable optical sensors.
  • the erasing process restores the original magnetic direction which existed prior to recording by the use of a vertical magnetic field of polarity opposite to that used for recording when accompanied by heating from the laser beam.
  • a vertical magnetic field of polarity opposite to that used for recording when accompanied by heating from the laser beam.
  • an electromagnet in which the current can be adjusted and reversed, (thereby changing the direction and/or intensity of the induced magnetic field) has been the preferred source for generating the magnetic bias for both the writing and the erasing.
  • the electromagnet in some cases, a reversible permanent magnet
  • the bias magnet is also sometimes referred to as the bias magnet.
  • Deguchi et al in U.S. Pat. No. 4,497,006, schematically describe in their disclosure an electromagnet surrounding the objective lens of their recording/playback apparatus which provides the bias magnetization required for magneto-optic operations.
  • Ota et al in U.S. Pat. No. 4,477,852, discloses a pair of bias electromagnets adjacent the objective lens in conjunction with a pair of lasers for performing the erase and re-write functions in a magneto-optic recording and reproducing system.
  • U.S. Pat. No. 4,466,004 also describes an electromagnet surrounding the objective lens, and records information by varying the field strength of the electromagnet in the areas of the media heated by a continuous laser beam. In the previous two examples, writing was accomplished by varying the intensity of the laser beam.
  • U.S. Pat. No. 4,610,009 assigned to the Xerox Corporation, describes a system wherein plural lasers operate through a single optical path and cooperate with bi-polar magnetic field producing means located on the opposite side of the magneto-optic medium.
  • This system also includes a bias electromagnet essentially concentric with the focusing electromagnet of the objective lens.
  • the deficiencies of these examples in providing an essentially vertical magnetic field coincident with the laser beam is addressed in U.S. Pat. No. 4,340,914 issued to Hanaoka and assigned to Olympus Optical.
  • This patent discloses an auxiliary magnetic pole piece for focusing a magnetic flux from the magnetic field generating device (bias magnet) into at least the heated portion and which is located on the side of the media opposite the laser beam.
  • This patent discloses a bias electromagnet configured in the shape of a letter "E", in which the top and bottom legs of the "E” extend radially from one edge of the media towards the center (when the media is in a disk configuration, the center leg of the “E” likewise extends from one edge towards the center, but on the opposite side of the media from the top and bottom legs).
  • Current carrying coils are wound about each of the two segments of the vertical portion of the "E” to magnetize the electromagnet.
  • Attached to the housing of the objective lens is a ring or cap of magnetic material which has a small hole in it to allow passage of the laser beam.
  • Magnetic coupling of this cap to the top and bottom legs of the "E” is accomplished by a pair of pole pieces, in effect, filling in the gap between the legs and the cap.
  • the pole pieces, the cap, and the objective lens can move radially in-between the top and bottom of the "E", with the return path of the magnetic flux being provided by the center leg which is located underneath the lens and the media.
  • the magnetic elements can conveniently be placed on the side of the media opposite the side upon which the laser impinges.
  • this opposite side location is not physically accessible, for example, when the magneto-optic media is supported on the surface of a drum, or is supported on a very thick substrate, these magnetic elements must be located on the same side of the media as the optics are.
  • the present invention describes an apparatus for providing a vertical bias magnetic field coincident with a read/write laser beam in a magneto-optic recording system. It comprises magnetizable material surrounding the end of an objective lens housing of the read/write/erase optical system and extending across the face of the objective lens housing proximate the recording media, a small hole in the magnetizable material extending across the face of said objective lens housing to permit the laser beam to pass through to the recording media, and an electromagnet coil closely surrounding said magnetizable material for purposes of generating the necessary magnetic field.
  • FIG. 1 is a longitudinal cross-sectional view of a first embodiment of the invention
  • FIg. 2 is a longitudinal cross-sectional view of a second embodiment of the invention.
  • FIG. 3 is a longitudinal cross-sectional view of a third embodiment of the invention.
  • FIG. 4 is a longitudinal cross-sectional view of a fourth embodiment of the invention.
  • FIG. 5 is a performance graph showing that the elements of the invention give results equivalent to those obtained from the conventional "backside" bias magnet location.
  • FIG. 1 illustrates in cross-section the principal components of the invention and their relationship to each other and to a recording medium.
  • An optical system 10 is located in close proximity to record medium 28 with the spatial relationship between them being defined as that necessary to allow radiation from a laser (not shown) to pass through, and along the optical axis 32 of an objective lens housing 11, through an objective lens 13, and eventually arriving, in sharp focus, upon the recording surface 25 of recording media 28.
  • the source of the laser beam 15 as well as the various optical components required to produce the sharp focus are well known in the art and need not be shown nor described here.
  • Means, not shown, provide relative movement of the record media 28 past the focus point 20 of the laser beam 15 so that controlled modulation of the laser will cause successive detectable changes to be generated in the recording surface 25.
  • lens housing 11 may also support a transparent lens cover glass 14, which is employed to modify the focal length of the lens and to adapt a specific lens design for use with different media constructions.
  • electromagnet assembly 29 Surrounding the lens housing 11 at the end in proximity with the recording surface 25, is an electromagnet assembly 29, comprising multiple turns of wire 18 wound around a core 17 of ferromagnetic material such as soft iron.
  • Wire retaining means can consist of so-called potting compounds which serve to both position the wires and define the outer dimensions of the coil assembly.
  • the shape and dimensions of the inside of the electromagnet 29 are configured to provide only enough physical clearance with the lens housing 11 to allow unhindered motion of the lens housing as required to allow the aforementioned focusing movement. This minimum clearance allows optimization of the magnetic coupling between the electromagnet 29 and the lens housing 11 for reasons that will be described later, and is preferably in the range of 0.127-0.381 mm total clearance.
  • Wire leads 27 serve to carry electrical energy from power supply 26 and means (not shown) exist to establish the proper direction of the magnetic field generated by the electromagnet 29 by controlling the direction of current flow through the electromagnet 29.
  • the lens housing 11 itself can be formed of iron or other magnetizable metallic alloys that have low retentivity, such as Permalloy.
  • the lens housing can be of brass with magnetizable material 12 applied by electroplating, by vacuum deposition, or by any of the other common and well known methods of metal deposition.
  • the magnetizable material 12 being deposited must extend around and over both the periphery and the end of the lens housing.
  • that portion of the magnetizable material which extends across the face of the lens housing may be secured not to the lens housing but to the end of the electromagnet core 17 which is located proximate to the recording media.
  • This portion of the magnetizable material, 41 in FIG. 3 may be a disk, separate from, but attached to, the electromagnet core, or it may be an integral part of the electromagnet core, formed during the manufacture of the electromagnet core.
  • the objective lens housing 11 must have clearance between its end and the disk 41, as well as clearance 21 between it and the inside surface of the electromagnet 29.
  • an aperture diameter of about 1.25 mm is deemed suitable for optic systems in common usage today, but other diameters may be appropriate as technology advances and designs change.
  • the aperture 19 may be slightly larger, or may be elongated in one direction to accommodate tracking movements of the laser beam optical system.
  • This electromagnet was then positioned concentrically around the objective lens housing described earlier, both attached to the Olympus single-axis optical head, and mounted approximately 1 mm away from the surface of a magneto-optical recording media disk, with the centerline of the laser beam perpendicular to the plane of the media.
  • the modified optical head described above was then installed on an automated optical disk tester which is capable of programming such variables as disk rotational speed, laser power, magnetic bias field intensity, recording frequency, and of measuring performance factors such as signal playback amplitude, carrier-to-noise ratio, and harmonic frequency content of the playback signal.
  • the magneto-optic media used was a 133 mm diameter disk manufactured by 3M Company, St. Paul, Minnesota. Media performance was measured first using a conventional backside electromagnet as the magnetic bias field source during recording on the disk. Since second harmonic distortion of a playback signal is the most sensitive indicator of magnetic bias effectiveness, the distortion level was measured while the magnetic bias level was changed over a range which produced a lowest....dip in distortion level, as shown in curve A of FIG.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Recording Or Reproducing By Magnetic Means (AREA)
US07/311,457 1989-02-16 1989-02-16 System for applying a perpendicular magnetic field to the illuminated side of a magneto-optic medium Expired - Fee Related US5022018A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US07/311,457 US5022018A (en) 1989-02-16 1989-02-16 System for applying a perpendicular magnetic field to the illuminated side of a magneto-optic medium
CA002008019A CA2008019A1 (en) 1989-02-16 1990-01-18 Magneto-optic recording system
DE69016055T DE69016055D1 (de) 1989-02-16 1990-02-13 Magnetooptisches Aufzeichnungssystem.
EP90301485A EP0383526B1 (de) 1989-02-16 1990-02-13 Magnetooptisches Aufzeichnungssystem
KR1019900001722A KR900013473A (ko) 1989-02-16 1990-02-13 자기광학 레코딩 시스템
JP2035070A JPH02247849A (ja) 1989-02-16 1990-02-15 情報を読出し、記録しまたは消去するための光学系

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US07/311,457 US5022018A (en) 1989-02-16 1989-02-16 System for applying a perpendicular magnetic field to the illuminated side of a magneto-optic medium

Publications (1)

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US5022018A true US5022018A (en) 1991-06-04

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US07/311,457 Expired - Fee Related US5022018A (en) 1989-02-16 1989-02-16 System for applying a perpendicular magnetic field to the illuminated side of a magneto-optic medium

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US (1) US5022018A (de)
EP (1) EP0383526B1 (de)
JP (1) JPH02247849A (de)
KR (1) KR900013473A (de)
CA (1) CA2008019A1 (de)
DE (1) DE69016055D1 (de)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5193082A (en) * 1989-03-31 1993-03-09 Sharp Kabushiki Kaisha Optical/magnetic composite head having magnetic and optical heads in one integrated unit
US5197050A (en) * 1989-10-06 1993-03-23 Fuji Xerox Co., Ltd. Flying head for a magneto-optical recording drive
US5247496A (en) * 1990-04-28 1993-09-21 Sony Corporation Recording and/or reproducing apparatus for using magneto-optical disc
US5287334A (en) * 1989-07-29 1994-02-15 Sony Corporation Magneto-optical pickup apparatus and magneto-optical recording/reproducing apparatus
US5367508A (en) * 1993-02-10 1994-11-22 Seiko Epson Corporation Magnetic field generation mechanism for magneto-optical recording
US5440530A (en) * 1991-05-07 1995-08-08 Commissariat A L'energie Atomique Integrated magneto-optical having a magnetic head set back from an optical head
US5544131A (en) * 1993-05-14 1996-08-06 Commissariat A L'energie Atomique Magnetic writing head for magneto-optical recording with thick protective coating
USRE35608E (en) * 1990-04-28 1997-09-16 Sony Corporation Recording and/or reproducing apparatus for using magneto-optical disc
US5784343A (en) * 1990-01-31 1998-07-21 Sony Corporation Magneto-optical recording and/or reproducing apparatus having a plurality of optical systems
WO1998048409A3 (en) * 1997-04-18 1998-12-17 Read Rite Corp Electro-magnetic coil assembly
US5886959A (en) * 1997-04-18 1999-03-23 Read-Rite Corporation Thin-film electro-magnetic coil design for use in a flying magneto-optical head
US5903525A (en) * 1997-04-18 1999-05-11 Read-Rite Corporation Coil for use with magneto-optical head
US5978319A (en) * 1997-11-06 1999-11-02 Read-Rite Corporation Thin electro-magnetic coil assembly for attachment to a slider
US6226233B1 (en) 1996-07-30 2001-05-01 Seagate Technology, Inc. Magneto-optical system utilizing MSR media
US6278666B1 (en) 1997-09-29 2001-08-21 Matsushita Electric Industrial Co., Ltd. Magneto-optical disk recording and reproducing device
US20080024024A1 (en) * 2006-07-28 2008-01-31 Nidec Corporation Motor and method of manufacturing thereof
US20100165822A1 (en) * 2008-12-31 2010-07-01 Hamid Balamane Thermally assisted recording head having recessed waveguide with near field transducer and methods of making same

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0550096B1 (de) * 1991-12-30 2004-08-04 Koninklijke Philips Electronics N.V. Magnetooptische Abtasteinrichtung
JPH11335269A (ja) 1998-05-19 1999-12-07 Hisamitsu Pharmaceut Co Inc 遺伝子関連医薬の経口投与固形製剤
JP4033082B2 (ja) 2002-11-07 2008-01-16 株式会社村田製作所 Ｄｃ−ｄｃコンバータ

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US4466004A (en) * 1981-01-05 1984-08-14 Ricoh Company, Ltd. Thermomagnetic recording
JPS59148159A (ja) * 1983-02-15 1984-08-24 Canon Inc 光ピツクアツプ装置
US4477852A (en) * 1981-03-28 1984-10-16 Kokusai Denshin Denwa Kabushiki Kaisha Magneto-optical recording and reproducing system
US4497006A (en) * 1981-02-06 1985-01-29 Sharp Kabushiki Kaisha Magneto-optic recording/playback head assembly
JPS60214439A (ja) * 1984-04-11 1985-10-26 Seiko Epson Corp 光磁気ヘツド
JPS60214438A (ja) * 1984-04-11 1985-10-26 Seiko Epson Corp 光磁気ヘツド
JPS60261052A (ja) * 1984-06-06 1985-12-24 Fujitsu Ltd 光磁気デイスク用光学ヘツド
US4610009A (en) * 1983-05-23 1986-09-02 Xerox Corporation Writing, erasing and readout system for a magneto-optic recording medium
US4660190A (en) * 1983-01-25 1987-04-21 Sharp Kabushiki Kaisha Optical focus position control in optical disc apparatus
US4701894A (en) * 1986-03-28 1987-10-20 Rca Corporation Magnetic biasing apparatus for magneto-optic recording including a magnetic circuit
US4803674A (en) * 1985-11-20 1989-02-07 Hitachi, Ltd. Magneto-optical recorder with small-sized, low-powered electromagnetic coil
US4868802A (en) * 1986-07-28 1989-09-19 Kabushiki Kaisha Toshiba Magnetooptic recording and erasing head which performs biasing, tracking and focusing

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US4340914A (en) * 1979-03-22 1982-07-20 Olympus Optical Co., Ltd. Thermomagnetic recording and reproducing apparatus
US4466004A (en) * 1981-01-05 1984-08-14 Ricoh Company, Ltd. Thermomagnetic recording
US4497006A (en) * 1981-02-06 1985-01-29 Sharp Kabushiki Kaisha Magneto-optic recording/playback head assembly
US4477852A (en) * 1981-03-28 1984-10-16 Kokusai Denshin Denwa Kabushiki Kaisha Magneto-optical recording and reproducing system
US4660190A (en) * 1983-01-25 1987-04-21 Sharp Kabushiki Kaisha Optical focus position control in optical disc apparatus
JPS59148159A (ja) * 1983-02-15 1984-08-24 Canon Inc 光ピツクアツプ装置
US4610009A (en) * 1983-05-23 1986-09-02 Xerox Corporation Writing, erasing and readout system for a magneto-optic recording medium
JPS60214439A (ja) * 1984-04-11 1985-10-26 Seiko Epson Corp 光磁気ヘツド
JPS60214438A (ja) * 1984-04-11 1985-10-26 Seiko Epson Corp 光磁気ヘツド
JPS60261052A (ja) * 1984-06-06 1985-12-24 Fujitsu Ltd 光磁気デイスク用光学ヘツド
US4803674A (en) * 1985-11-20 1989-02-07 Hitachi, Ltd. Magneto-optical recorder with small-sized, low-powered electromagnetic coil
US4701894A (en) * 1986-03-28 1987-10-20 Rca Corporation Magnetic biasing apparatus for magneto-optic recording including a magnetic circuit
US4868802A (en) * 1986-07-28 1989-09-19 Kabushiki Kaisha Toshiba Magnetooptic recording and erasing head which performs biasing, tracking and focusing

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5193082A (en) * 1989-03-31 1993-03-09 Sharp Kabushiki Kaisha Optical/magnetic composite head having magnetic and optical heads in one integrated unit
US5287334A (en) * 1989-07-29 1994-02-15 Sony Corporation Magneto-optical pickup apparatus and magneto-optical recording/reproducing apparatus
US5197050A (en) * 1989-10-06 1993-03-23 Fuji Xerox Co., Ltd. Flying head for a magneto-optical recording drive
US5784343A (en) * 1990-01-31 1998-07-21 Sony Corporation Magneto-optical recording and/or reproducing apparatus having a plurality of optical systems
US5247496A (en) * 1990-04-28 1993-09-21 Sony Corporation Recording and/or reproducing apparatus for using magneto-optical disc
USRE35608E (en) * 1990-04-28 1997-09-16 Sony Corporation Recording and/or reproducing apparatus for using magneto-optical disc
US5440530A (en) * 1991-05-07 1995-08-08 Commissariat A L'energie Atomique Integrated magneto-optical having a magnetic head set back from an optical head
US5367508A (en) * 1993-02-10 1994-11-22 Seiko Epson Corporation Magnetic field generation mechanism for magneto-optical recording
US5544131A (en) * 1993-05-14 1996-08-06 Commissariat A L'energie Atomique Magnetic writing head for magneto-optical recording with thick protective coating
US5642336A (en) * 1993-05-14 1997-06-24 Commissariat A L'energie Atomique Magnetic writing head for magneto-optical recording with thick protective coating
US6226233B1 (en) 1996-07-30 2001-05-01 Seagate Technology, Inc. Magneto-optical system utilizing MSR media
WO1998048409A3 (en) * 1997-04-18 1998-12-17 Read Rite Corp Electro-magnetic coil assembly
US5903525A (en) * 1997-04-18 1999-05-11 Read-Rite Corporation Coil for use with magneto-optical head
US5886959A (en) * 1997-04-18 1999-03-23 Read-Rite Corporation Thin-film electro-magnetic coil design for use in a flying magneto-optical head
US6278666B1 (en) 1997-09-29 2001-08-21 Matsushita Electric Industrial Co., Ltd. Magneto-optical disk recording and reproducing device
US5978319A (en) * 1997-11-06 1999-11-02 Read-Rite Corporation Thin electro-magnetic coil assembly for attachment to a slider
US20080024024A1 (en) * 2006-07-28 2008-01-31 Nidec Corporation Motor and method of manufacturing thereof
US20100165822A1 (en) * 2008-12-31 2010-07-01 Hamid Balamane Thermally assisted recording head having recessed waveguide with near field transducer and methods of making same
US8169881B2 (en) 2008-12-31 2012-05-01 Hitachi Global Storage Technologies Netherlands B.V. Thermally assisted recording head having recessed waveguide with near field transducer and methods of making same
US8619535B2 (en) 2008-12-31 2013-12-31 HGST Netherlands B.V. Thermally assisted recording head having recessed waveguide with near field transducer and methods of making same

Also Published As

Publication number Publication date
JPH02247849A (ja) 1990-10-03
EP0383526A3 (de) 1991-09-04
DE69016055D1 (de) 1995-03-02
KR900013473A (ko) 1990-09-05
EP0383526B1 (de) 1995-01-18
EP0383526A2 (de) 1990-08-22
CA2008019A1 (en) 1990-08-16

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